It is sometimes necessary to field-sever pipes, columns, and the like in a variety of endeavors. For example, in the exploration/production of off-shore oil and natural gas, it may be necessary periodically to abandon a particular exploration/production site and relocate the associated off-shore platform due to exhaustion of the oil and gas field and/or changed economic conditions which mitigates against continued exploration/production at a particular site. Relocation of the off-shore platform, however, cannot occur until all of the well casings extending from the underwater floor have been severed at a height where they would not present an obstacle to mariners, especially nets which are trawled by fisherman.
The well casings which are employed in the off-shore exploration/production of oil and natural gas, however, are typically thick composite-walled structures to prevent casing rupture and the environmental devastation which could ensue. That is, it is not uncommon for a single well casing to be composed of several sleeved pipes of increasing diameters with the space between adjacent ones of the pipes being filled with reinforcing cementation. Special difficulties in addition to the underwater environment are thus presented when an attempt is made to sever such well casings due to their relatively thick-walled structure.
While a variety of pipe machining/cutting tools and so-called pipe lathes are well known in the art (see, for example, U.S. Pat. Nos. 3,848,489 to Santana; 4,213,357 to Lively et al; 4,665,782 to VanderPol; 4,754,672 to VanderPol; 4,739,685 to Ricci; and 4,944,205 to Ricci), they are deficient in terms of their ability to cut relatively thick-walled tubular articles of the type typically encountered in connection with underwater well casings. That is, to the best of the present inventor's knowledge, none of the prior art devices are capable or could obviously be modified to function in the manner demanded when underwater thick-walled well cases are to be cut.
What has been needed in this art therefore, is a cutting tool which has the ability to reliably cut and sever relatively thick-walled tubular members (e.g., underwater composite well casings, as well as hollow or solid tubular support columns formed of metal, cement or the like). It is towards providing such a tool that the present invention is directed.
Broadly, the present invention is embodied in a tool having a cutting assembly which is both orbitally and radially movable relative to a central longitudinal axis of the tubular member being cut, whereby the cutting bit and associated support structures of the cutting assembly have an extent of radial travel and a structural configuration which allow for bit movement sufficient to cut relatively thick-walled tubular members (e.g., to, and preferably at least slightly through, the longitudinal center of the tubular member).
More specifically, the present invention is embodied in a cutting tool for cutting thick-walled tubular members which includes a stationary annular frame and a radial cutting assembly which is radially mounted on the frame for orbital movement about the tubular member being cut. The radial cutting assembly is itself provided with a cutting bit subassembly that is radially advanced into the tubular member in response to the cutting assembly's orbital movement.
A cutting bit is carried forwardly of a radially movable bit support block. As viewed in relation to the longitudinal axis of the tubular member being cut, the cutting bit presents a cutting edge that has a greater dimension as compared to the following bit support block and associated structure. As such, the following supporting structure for the bit will establish passageways when the bit is advanced sufficiently into the tubular member being cut to conveniently allow for shavings and debris to be removed from the cutting face of the bit. Moreover, such established passageways allow lubricating/flushing fluid (e.g., water, oil or the like) to be admitted to the bit so as to assist in the cutting operation.
Further aspects and advantages will become evident from the following detailed description of the preferred exemplary embodiments thereof.